Checking if a file exist or not can be easily done with the script below

if [ -f "$FILE_PATH" ]; then
  # If the $FILE_PATH exist, code inside the block will get executed, for example:
  echo "File $FILE_PATH exist";
fi

Or to check if a file doesn't exist:

if [ ! -d "$FILE_PATH" ]; then
  # If the $FILE_PATH does not exist, code inside the block will get executed, for example:
  echo "File $FILE_PATH does not exist";
fi

Are you looking for the scenario if a directory exist or not in bash scripts?

There is also a shorthand notation to check if a file exist or not:

Shorthand to check if a file exist

[ -f "$FILE_PATH" ] && echo "File $FILE_PATH exist";

Shorthand to check if a file does not exist

[ ! -f "$FILE_PATH" ] && echo "File $FILE_PATH does not exist";

You can have any statement after the && symbol.

The above code is an ideal way to check if a path is a file or not.